Fabrication of efficient CuS/BiVO4 p-n heterojunctions for sensing and photo-reduction of Cr (VI)

Abstract

Applications in sensing and photo reduction of Cr (VI) by pristine BiVO4 are restricted because of the narrow band gap and easy electron-hole recombination. To overcome the issue, CuS is coupled to BiVO4indifferent molar ratios (1:1, 1:2, and 2:1) by hydrothermal synthesis and used in Cr (VI) sensing and photo-reduction. The tetragonal zircon phase of BiVO4 and hexagonal structure of CuS have been confirmed through XRD. Then n-type and p-type behavior of BiVO4 and CuS respectively have been shown from a Mott-Schotky study. The Current–Voltage characteristics of all the samples were found to be linear and ohmic in nature. The conduction and valence band position of BiVO4 (+0.33 eVand +3.08 eV) and CuS (-0.30 eV and +1.81 eV) ensures the development of p-n heterojunction and channelization of the photo-induced charge carriers. This helps in decreasing electron-hole recombination, thereby increasing the sensing efficiency (99%) and photo-reduction (98%) of Cr (VI) at a concentration of 40 ppm.